Precautions for the avoidance or elimination of contaminations or deposits, such as scale deposits, dirt and/or corrosion are of importance, specifically in apparatuses for the heating and vaporization of a fluid, especially of water, as in the case of vapor generators, in order to ensure cost-effective operation and maximum lifetime of the apparatus.
A number of devices are known in the state of the art, which provide information on the state of scale forming in apparatuses for the heating and vaporization of water, so that when scale is detected, measures for descaling can be undertaken.
For example, a reliable and, due to its simplicity, cost-effective device is known from German patent DE 199 12 444 C2. In this device, the degree of scale forming vapor generator of a cooking apparatus is determined, by evaluating the difference between a filling volume of a heat generator in the scale-free state and a filling volume after a number of fillings of the steam generator with calcium-containing water. When the difference exceeds a pre-determined value, it is assumed that a reduction of the filling volume occurred due to scale forming, and that descaling of the vapor generator is to be performed. Although with this device it can be determined reliably if a certain degree of scale is present in the apparatus, the device does not make it possible to perform a defined conducting of a cleaning or descaling operation. In particular, no conclusions can be drawn about a suitable dosage of cleaning agents, descaling agents, or water-softening agents.
A household device with a sensor for the determination of the hardness of the water is known from DE 20 2004 013 787 U1. According to this disclosure, a dosage of a water-softening agent that is fed continuously into a fluid in order to prevent the formation of scale is effected as a function of the water hardness determined with the hardness sensor. Such a continuous softening of the water, however, cannot be used in a cooking appliance since the softening agent would have an adverse influence on the cooking result. In a fluid-receiving device of a cooking appliance, therefore, the cleaning processes, specifically descaling processes must be performed independently of the cooking operation.
DE 102 59 829 A1 discloses a method and a device for descaling in vapor generators for cooking appliances. The device comprises a storage container, which is connected to a vapor generator via a connecting line. Within the connecting line, a device is provided that makes it possible to introduce a certain amount of descaling agent into the vapor generator at a predetermined moment in time. Depending on the duration of operation and/or on a determined degree of scale in the vapor generator, the descaling agent is introduced into the vapor generator. However, the disadvantage of this method is that the descaling process in the vapor generator cannot be performed with the disclosed device in such a way that it is adjusted in the best possible way to the existing environmental conditions and optimized in the best possible way so that overdosage of the descaling agent and thus unnecessary pollution of the environment, insufficient descaling or unnecessarily long scaling processes and thus unnecessarily long interruptions in the operation are avoided.